Evaluation of subcortical grey matter abnormalities in patients with MRI-negative cortical epilepsy determined through structural and tensor magnetic resonance imaging

Abstract

BackgroundAlthough many studies have found abnormalities in subcortical grey matter (GM) in patients with temporal lobe epilepsy or generalised epilepsies, few studies have examined subcortical GM in focal neocortical seizures. Using structural and tensor magnetic resonance imaging (MRI), we evaluated subcortical GM from patients with extratemporal lobe epilepsy without visible lesion on MRI. Our aims were to determine whether there are structural abnormalities in these patients and to correlate the extent of any observed structural changes with clinical characteristics of disease in these patients.MethodsTwenty-four people with epilepsy and 29 age-matched normal subjects were imaged with high-resolution structural and diffusion tensor MR scans. The patients were characterised clinically by normal brain MRI scans and seizures that originated in the neocortex and evolved to secondarily generalised convulsions. We first used whole brain voxel-based morphometry (VBM) to detect density changes in subcortical GM. Volumetric data, values of mean diffusivity (MD) and fractional anisotropy (FA) for seven subcortical GM structures (hippocampus, caudate nucleus, putamen, globus pallidus, nucleus accumbens, thalamus and amygdala) were obtained using a model-based segmentation and registration tool. Differences in the volumes and diffusion parameters between patients and controls and correlations with the early onset and progression of epilepsy were estimated.ResultsReduced volumes and altered diffusion parameters of subcortical GM were universally observed in patients in the subcortical regions studied. In the patient-control group comparison of VBM, the right putamen, bilateral nucleus accumbens and right caudate nucleus of epileptic patients exhibited a significantly decreased density Segregated volumetry and diffusion assessment of subcortical GM showed apparent atrophy of the left caudate nucleus, left amygdala and right putamen; reduced FA values for the bilateral nucleus accumbens; and elevated MD values for the left thalamus, right hippocampus and right globus pallidus A decreased volume of the nucleus accumbens consistently related to an early onset of disease. The duration of disease contributed to the shrinkage of the left thalamus.ConclusionsPatients with neocortical seizures and secondary generalisation had smaller volumes and microstructural anomalies in subcortical GM regions. Subcortical GM atrophy is relevant to the early onset and progression of epilepsy.

Connectivity‐based parcellation of the nucleus accumbens into core and shell portions for stereotactic target localization and alterations in each NAc subdivision in mTLE patients

“…Wang et al () investigated decreases and increases in FA in regions such as the entorhinal‐hippocampal area, amygdala, thalamus, striatum, accumbens, and neocortex in methionine sulfoximine‐infused rats as model of human MTLE. Peng et al () observed altered diffusion parameters of subcortical gray matter in patients with MRI‐negative cortical epilepsy using DTI, and reported the decrease in FA values in the bilateral nucleus accumbens in epilepsy patients for the first time. The decreases in FA using DTI are known to occur in gray matter areas during cerebral ischemia and sustained seizures.…”

“…Moreover, some recent clinical studies provided initial evidence for the safety and feasibility of chronic electrical stimulation of the NAc in patients with intractable partial epilepsy, as indicated by largely unchanged neurocognitive function and psychiatric comorbidity (Kowski et al, ; Schmitt et al, ). Peng et al () reported the first evidence of structural abnormalities in the nucleus accumbens along with other subcortical gray matter in patients with MRI‐negative extemporal lobe cortical epilepsy. These findings, together with our results, strongly support the role of the NAc shell in epileptogenesis from distinct perspectives.…”

Thalamocortical Tracts, but not the Putamen, Present Microstructural Abnormalities in Juvenile Myoclonic Epilepsy: A Diffusion Tractography Study

“…10,11,32,47,48 The same loops are implicated as anatomical correlates of myoclonus. 49 In a sample of 43 JME patients, 42% reported asymmetric or unilateral myoclonic jerks. 6 Interestingly, Peng et al found a reduced right putaminal volume in epileptic patients with normal brain imaging.…”

Imaging for Epilepsy Surgery

“…Quantitative imaging can also define the total volumes of gray and white matter in each lobe, which may also inform the trained observer that a subtle lobar abnormality exists that could not be appreciated on direct inspection. 15 Qualitative evaluation is currently in clinical use, while quantitative automated methods remain under investigation. 16,17…”